Milk frothing appliances are available in different types. Some milk frothing appliances, for instance, are integrated into coffee machines, while others are configured for stand-alone use.
An example of an integrated milk frothing appliance is the ‘steam wand’ that is customarily built-in in espresso machines. To froth milk, a steam outlet of the steam wand is positioned in a cup of milk, at or just below the surface of the milk. Then the steam wand is turned on so as to effect the ejection of a jet of steam that, as it impacts the air-milk interface, causes the production of an milk-air-steam mixture which results in the desired froth. A disadvantage of the steam wand is that its operation requires skill on the part of the user, in particular since the optimal position of the steam outlet relative to the milk surface is rather sensitive.
To simplify the production of milk froth, especially for home users, various dedicated stand-alone milk frothing devices have been developed. Some make use of an internal heatable tank for receiving a milk-based liquid, in which a rotatably drivable stirrer or whisk is positioned for whipping the liquid into a froth. Others mimic the operation of a steam wand, and include a modified, typically Venturi-based steam outlet nozzle that assists in the act of frothing by siphoning milk from a cup, mixing it with air and steam, and dispensing it back into the cup it came from.
Known dedicated milk frothing devices are typically electrically powered devices that include plenty of electronics. Besides a heater, such electronics may include an electric motor to drive the stirrer, or alternatively, in the case of a steam wand-mimicking device, a solenoid pump and several valves as part of a water dosing system configured to deliver water successively to the electric heater and an outlet of the steam wand. In addition, the milk frothing device may include internal electronics such as a central controller that controls the operation of the entire device, and for example allows a user to set certain operating parameters—e.g. heater temperature, whisking time, steam quantity, etc.—in dependence of the liquid to be frothed and its volume. The device may further be fitted with a plurality of external controls to enable a user to input the desired parameters.
The electronic components in known milk frothing devices make their manufacture rather costly, and their operation in generally humid kitchen environments susceptible to failure. The risk of moist-induced defects is particularly imminent for stirrer-type frothers, of which at least the internal liquid tank must be thoroughly cleaned after each use to maintain the hygiene of the device. Furthermore, the external user controls necessary to operate the full functionality of milk frothing device may normally be positioned on an outside of the device and, and may so mar an otherwise aesthetically pleasing, stylishly clean appearance.